1. Field of the Invention
This invention relates to electronic circuitry used to generate, store, and transmit information and more particularly to electronic circuitry that can do so by representing such information in any chosen digital number system, especially ternary (based on the number three) to provide multiple-valued logic.
2. Description of the Related Art
Computers, especially personal computers, are now quite common. The development history and construction of such computers is well documented and readily available through textbooks, treatises, and other written sources. A brief summary is given here as background for the invention set forth herein.
Since the arrival of the transistor and the chip-based microcircuit, information is increasingly represented in an electronic form. Electronic representation of information is very powerful as the information is no longer tied to the particular individual thing used to convey the information (although it may be tied to the particular medium). For example, books store information as printed words physically attached to the pages. The words in the book cannot easily be transferred or copied from one book to another book. In contrast, computers and other electronic data machines (referred to generally as "computers" herein) store their information as voltages that can be duplicated and/or transmitted very quickly and easily to other computers.
Furthermore, computers can operate on their stored data/information by instructions that are also stored electronically. Sequences of these instructions are "computer programs" that are created to perform a certain set of instructions. Such sequences may easily be repeated on the same or different sets of data/information. In the last fifteen years, the flexibility and power of computer programs has increased to the point where off-the-shelf programs are over several million bytes (several megabytes) long and to where the graphical representation of moving objects in an environment (as in virtual reality) is increasingly available.
One of the great advantages of today's computers is the speed at which they operate. Off-the-shelf microcomputers can operate at speeds of 200 megahertz (MHz) or more and can perform millions of instructions per second. Increasing operating speeds are becoming more readily available as time goes on and at lower prices. Modern day computers require such speed as the increased size of more powerful and flexible software requires greater performance from the hardware. Ultimately, the speed of a computer is determined by the response time of the individual circuits and the circuit density limit at which no additional circuits can fit into a unit space. The faster the circuit response time and the greater the circuit density, the better and faster the computer. However, there are limits to which circuit response and density can currently be increased. These limits foil attempts to increase the utility and speed of computers.
To use and manipulate voltages that store, convey, and operate upon information, computers use logic circuits in a predetermined fashion. Currently, most logic circuits are based on a binary number system in order to convey and manipulate information. The reason for this may be historical as early transistorized logic circuits were based on an "on-off" type of data storage. That is to say, an "on" state or a presence of voltage represented one value ("one") while an "off" state or absence of voltage represented another value ("zero"). Previous logical circuit structures addressing the fabrication of circuits that synthesize binary logic include: ECL, TTL, DTL, RTL, NMOS, PMOS, and COS-MOS or CMOS.
In committing to binary circuitry, the computer industry exploited the basic operating state of the transistor. Transistors operate in two basic states by either transmitting voltage and current through the transistor or by preventing such transmission. However, by committing to binary logic, the computer industry imposed an unnecessary limitation on computer speed and utility.
Binary logic limits computer speed as it is the least dense and most elaborate manner in which information can be digitally represented. Unlike the decimal number system of common use that can represent any one of ten numbers in any decimal place, the binary number system can represent only one of two numbers in any binary place. For example, the number one hundred requires only three digits in the decimal number system, namely "100". However, in the binary number system, the number one hundred is represented as "1100100"(2.sup.6 +2.sup.5 +2.sup.2 =64+32+4). In binary, the numeral "100" represents the number four. What takes three numeral places in decimal takes seven places in binary, an over-100% increase in numeral places.
While a number system based on the number ten is convenient for modern-day use, other number systems have been used in the past. The number sixty formed the basis of a number system used in ancient Sumeria and Babylon. The number twenty formed the basis of the Mayan number system. What may form a convenient basis for a number system for people may not necessarily form a convenient number system for computers. Mechanical and structural constraints dictate what number system is the most convenient. Unfortunately, with binary-based logic circuitry, modern-day computers cannot adapt to incorporate and use what number system(s) might be the most advantageous.
As such, binary logic circuits require more physical space and necessarily operate at less-than-optimum speeds. It would be very advantageous to provide computer logic circuits that operate in an optimum number system, e.g., based upon the number three, four, or five, etc. so that logic operations could proceed more quickly and efficiently. Such an optimum number system may depend upon the use to which the computer (or pertinent circuitry) is put.
Previously, there have been few circuits capable of directly synthesizing an information-representing logic system based on a number system other than two. What circuits there might be are primarily ternary (based on the number three (3)) and are passively loaded, inhibiting their ultimate utility for use in computers. Also, most of these circuits are mere translators that use two or more binary inputs to produce only one digit of n-valued output, or vice versa (n being any chosen number). Such translators do not use the power inherently present in representing information in a number system greater than two. Furthermore, such translators cannot be used in a systematic and efficient manner in order to construct a computer implementing a number-based logic system other than one based upon the number two.
While translating circuitry is functional, it is extremely limiting in both cost and size. Also, the detection and elimination of disallowed binary and/or n-valued states further increase such cost and size.
Recently, Intel Corporation announced the availability of flash memory with storage elements using more than two states, indicating the commercial viability of multiple-valued logic circuits in the marketplace.
The inventor of SUS-LOC previously patented a tristable multivibrator used to generate the three signal levels used in ternary data systems. That patent, U.S. Pat. No. 4,990,796 issued to Olson on Feb. 5, 1991 is incorporated herein by this reference. That tristable multivibrator only used enhancement mode Insulated Gate Field Effect Transistors (IGFETs) and resistive elements to accomplish its signal goals. No depletion mode IGFETs were used. Such depletion mode IGFETs have apparently been generally unavailable on the open market and are generally absent from most current circuit designs.